Liposomes are microscopic particles that are made up of one or more lipid bilayers enclosing an internal compartment. Liposomes can be categorized into multilamellar vesicles, multivesicular liposomes, unilamellar vesicles and giant liposomes. Liposomes have been widely used as carriers for a variety of agents such as drugs, cosmetics, diagnostic reagents, and genetic material. Since liposomes consist of non-toxic lipids, they generally have low toxicity and therefore are useful in a variety of pharmaceutical applications. In particular, liposomes are useful for increasing the circulation lifetime of agents that have a short half-life in the bloodstream. Liposome encapsulated drugs often have biodistributions and toxicities which differ greatly from those of free drug. For specific in vivo delivery, the sizes, charges and surface properties of these carriers can be changed by varying the preparation methods and by tailoring the lipid makeup of the carrier. For instance, liposomes may be made to release a drug more quickly by decreasing the acyl chain length of a lipid making up the carrier. However, conventional liposomes are not stable enough for oral administration of a bioactive agent, as the liposomes cannot withstand the harsh in vivo environments and degrade resulting in the bioactive agent being destroyed.
Thus, there is a need in the art for liposomes having the required stability for the oral delivery of a bioactive agent. The present invention addresses this unmet need in the art.